1. Field of the Invention
Embodiments of the present invention generally relate to respiration. More specifically, the present invention relates to an apparatus and method for stimulating respiration during sleep.
2. Description of the Related Art
A clinical pathologic entity called Sleep Apnea syndrome (SAS) affects many individuals around the world. Sleep apnea means “cessation of breath.” It is characterized by repetitive stops of respiration, each lasting for more than about 10 seconds, which brings the brain into a hypoxic state (reduced arterial oxygen tension). SAS may cause severe disturbances of sleep itself and may have deleterious effects on mental activities, such as intellectual performance, memory, and behavior. Further, SAS is known as one of the causes of cardiovascular diseases, increased blood pressure (hypertension), stroke, heart arrhythmia, and conduction disturbances which may lead even to fatal cardiac arrest. SAS is especially dangerous in patents having chronic lung and heart diseases.
Many patients are at risk of suffering from SAS. Certain populations of patients are at higher risk than others. For instance, 30% of the middle-aged population, mainly men, suffers from respiratory disturbances during sleep. Additionally, frequent sleep apneas are found in about 50% of cardiovascular patients. Furthermore, there are many more patients with “unrecognized” SAS, since only direct observation of the respiratory cycle of a patient during sleep can reveal this pathology.
There are essentially two main types of apnea. One type relates to stops in respiration during sleep caused by cessation or reduction of nerve stimuli extending from the respiratory center in the brain to respiratory muscles. This type of apnea is commonly referred to as central apnea. The second type of apnea relates to the uncontrolled excessive decrease of muscle tone in the upper airway resulting in obstruction. This type of apnea is commonly referred to as obstructive apnea. The incomplete obstruction of the upper airway usually causes snoring. Frequently, patients have a combination of central and obstructive apneas, which is referred to as mixed apnea.
Obstructive apnea is caused by the abnormal, excessive reduction of muscle tone of the oropharynx, pharynx, and hypopharynx; the retraction of the tongue; and negative pressure in nasal space which independently or collectively can result in the collapse and obstruction of the upper airway. Generally, the oropharyngeal muscles maintain the upper airway passage open in order to allow a normal breathing. As such, the reduction of muscle tone of oropharyngeal muscles is one of the main mechanisms of SAS.
A common means of protection against SAS is usually arousal from the sleep and restoration of normal breathing as a result of temporary normalization of the cortical neural control of respiration. However, as expected, these repetitive arousals result in fragmented disturbed sleep.
Current treatments of SAS have been limited to mechanical stenting of the airway via CPAP (continuous positive airway pressure) devices and oral appliances; and surgical procedures aimed at removing, reducing, repositioning, or stiffening tissue in the upper airway. CPAP and oral devices have a 50%-60% compliance rate because of patients' feelings of claustrophobia, nasal stuffiness, and inconvenience related to these devices' awkward and cumbersome equipment. Surgical treatments are usually very painful, require the use of general anesthesia, and can have severe complications. In the medical literature, surgical interventions are at best 60-70% effective at curing sleep apnea.
The most widely used device is the CPAP, which prevents collapse of the pharynx by blowing air into the upper airway tract. However, the CPAP device has several substantial shortcomings. For instance, the CPAP device tends to be uncomfortable and noisy. Further, the CPAP device requires the use of a mask on the face of the patient, preventing free movement during sleep. Additionally, the inflow of the air pressure during the use of the CPAP device sometimes causes the sensation of suffocation, nasal drying, and even pain in the ears due to barotrauma. Furthermore, the regulation and tuning of the CPAP device requires time and observation. As a result, patient compliance is the greatest hurdle with the CPAP device and the CPAP device rarely gets above a 60% compliance rate.
Therefore, there remains a need for a device to aid in the restoration of normal breathing to SAS patients that is simple to use, comfortable, non-invasive, painless, and does not cause the sensation of suffocation or nasal drying.